feat(lanes): wait_distill — block until the next distill batch, no polling

The harness re-invokes the main loop when a background command exits, so a blocking
wait IS the self-reminder; a sleep-then-tail poll loop would just burn tokens for the
same information.

tools/lanes/wait_distill.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+# Blocks until the distill lane raises the NEXT batch, then exits — the harness re-invokes the main
+# loop on completion, so this is a self-reminder without polling (no sleep-then-tail loops).
+set -u
+cd /home/musashi/bfm-decomp
+DEADLINE=$(( $(date +%s) + 10800 ))          # 3h, then report back regardless
+while [ -z "$(ls .run/distill_ready/*.json 2>/dev/null)" ]; do
+  [ "$(date +%s)" -ge "$DEADLINE" ] && { echo "[wait_distill] 3h with no new batch — lane may be idle"; exit 0; }
+  [ -e .run/ox_campaign.stop ] && { echo "[wait_distill] campaign stopped"; exit 0; }
+  sleep 60
+done
+echo "[wait_distill] BATCH READY: $(ls .run/distill_ready/*.json)"
+.venv/bin/python -c "
+import json,glob
+for p in glob.glob('.run/distill_ready/*.json'):
+    d=json.load(open(p)); print(f\"  waves {' '.join(d['waves'])} · {d['novel']} novel candidates\")"